This invention relates to an apparatus and method for inspection and examination of bodies using ultrasonics, and more particularly, to an improved detector cell.
In many industrial and medical situations, it is desirable to examine the interior of a body for flaws or discontinuities. For example, industrially it is desirable to locate potential failure-initiating flaws and remove the product or part before it is used or to prevent its continued use. In medical situations, it is desirable to non-invasively examine internal organs and/or examine for tumors, etc. Presently ultrasound is used extensively in medicine to examine unborn fetus, tumors, etc.
One type of apparatus for ultrasonic non-destructive inspection is disclosed in U.S. Pat. No. 3,766,775 to Gunkel. Commerical ultrasonic inspection is based upon pulse-echo technology, whereby an ultrasonic signal or pulse is directed into a body, its echoes or reflections from the body are received and then electronically analyzed to establish an image. The images are then displayed using a cathode ray tube (CRT) or graphically plotted using an x-y plotter to develop what is referred to as an A-scan, B-scan or C-scan, etc.. Such an image will take a substantial length of time to develop, due to the considerable amount of time involved in scanning the body with the ultrasonic beam, this is particularly true if the body is large. Computers have been used to speed this process, but at the expense of sophisticated signal processing and cost. Furthermore, the images developed require a great deal of operator interpretation and operator skill to generate.
The equipment that is generally used in pulse-echo systems includes an ultrasonic transducer, complex signal processing equipment and complex image generating equipment. This equipment is large, does not easily lend itself to field use, and is not convenient for use in hand-held or hand-carried applications.
Proposals have been made in the past to use nematic liquid crystal materials as a detector in ultrasonic inspection systems. See, for example, U.S. Pat. No. to Dreyer, 3,597,043; Dreyer, U.S. Pat. No. 3,991,606; Kessler, et. al., U.S. Pat. No. 3,707,323; Greguss, U.S. Pat. No. 3,831,434.
Brenden, U.S. Pat. No. 3,879,989 uses cholesteric liquid crystals. For related art, also Kamei et al., U.S. Pat. No. 3,972,733; Wreford U. S. Pat. No. 3,137,837; Woodmansee U.S. Pat. No. 3,511,086 Sharpless U.S. Pat. No. 3,647,279; Mailer U.S. Pat. No. 3,837,423; Kamei et al. U.S. Pat. No. 3,972,733. A proposal to use an electro-optic system with liquid crystal display devices, and more particularly with a mixture of nematic and cholesteric liquid crystals, is disclosed in Cole, et. al., U.S. Pat. No. 3,984,343. See also publications by Bartolino et al., Jour. Appl. Physics, Vol. 46, No. 5, May 1975, p. 1928 et seq; Greguss, Acustica, Vol. 29 (1973), S. Hirzel Verlag, Stuttgart. p. 52 et seq; Nagai et al., Revue De Physique Appliquee, Vol. 12, No. 1 (January 1977) pp. 21-30.
If any of the patented or published systems had been successful, they would have eliminated the need for the complex signal processing and image forming equipment. However, the fact is that there are no commercially available ultrasonic inspection systems which provide an acceptable real time, liquid crystal, acousto-optical display. It is believed that none of the prior proposals has been capable of providing a commercially or medically acceptable image, and it is believed that none of the devices disclosed had acceptable perfomance characteristics such as sensitivity, contrast, response time, and resolution.
In my copending U.S. patent application, Ser. No. 232,247 filed Feb. 6, 1981, there is disclosed an improved ultrasonic imaging cell in which the ultrasonic signal from a body can be viewed directly and which includes a pair of cell covers, or substrates, with a nematic liquid crystal sealed therebetween. The cell covers are acoustically matched to their surrounding medium so as to minimize signal loss and so as to enhance the image. That application discloses laminated glass cell covers as a specific embodiment in which the thickness of the laminated layers is critically related to the wavelength of sound propagating therethrough.
The laminated structure of said co-pending application, Ser. No. 232,247 provides a siqnificant advance over the prior cell structures as disclosed in the Dreyer, Kessler, et. al., Greguss and Brenden prior art patents. However, the laminated structures require careful fabrication, and while they are functionally far superior to the existing prior art technology, it is desirable to provide a cell which is less expensive to fabricate and more easily fabricated, but which still has the desired acousto-optic properties.
Also, since filing my said co-pending application, Ser. No. 232,247, further research has led to significant discoveries that have permitted identification of factors that are, in my view, important to the production of an operative acousto-optical system, and cell, for detection and real-time imaging of concealed flaws, internal structures, and other similar matters, that are the natural intended subject of non-destructive and non-invasive testing of bodies, both inanimate and animate.
Thus, one object of this invention is to disclose an improved system, and an improved liquid crystal cell for use in an acousto-optic system, for non-destructive and non-invasive examination and testing of bodies, including concealed portions of said bodies, so as to provide a real-time image of the results of such testing.
Other objects of this invention will become apparent from the following description of the discoveries and in the appended claims.